The present invention relates to a pulse oximeter and a method of measuring the capillary refilling time, and more particularly to a pulse oximeter which, in addition to a calculation function that is provided in a related-art pulse oximeter and that calculates the blood oxygen saturation of an artery or the pulse rate based on pulse waves acquired from periodic variation components of the reception light intensities in the case where at least two light beams of different wavelengths are transmitted through or reflected from living tissue, includes a calculator that detects variations of the reception light intensities due to release of a state where the living tissue is pressed and that calculates the capillary refilling time, and also to a method of measuring the capillary refilling time.
In a related art, the capillary refilling time (CRT) is acquired in the manner in which a finger tip of the subject is pressed, the pressing is then released, the color of the skin after releasing is visually checked, and the time elapsed until the original color is regained is measured. However, such a visual measurement has poor quantitative performance, and an error due to a user easily occurs. Therefore, an apparatus has been proposed in which a finger tip is inserted into a probe having a clip-like shape, the finger tip is pressed by an actuator incorporated in the probe, and, when the pressing is then released, the capillary refilling time is detected (see U.S. Patent Application Publication No. 2007/0282182).
The measurement of the capillary refilling time is often performed in an emergency situation such as a case where an unconscious patient is transported by ambulance, and therefore easiness of measurement, and operation in parallel with other measurement are required in addition to measurement accuracy. In the related-art apparatus disclosed in U.S. Patent Application Publication No. 2007/0282182, although special devices such as the actuator is necessary and therefore preparation for measurement and measurement itself require a prolonged time, the possible measurement is substantially limited only to measurement of the capillary refilling time. Therefore, the apparatus is not popularly used at emergency sites where an emergency medical person is accustomed to performing rapid visual measurement.